Reaction product of hydrocarbylmonolithium and 1 3-butadiene as polymerization initiator

ABSTRACT

SEC- OR TERT-ORGANOMONOLITHIUM COMPOUNDS ARE REACTED WITH 1,3-BUTADIENE IN THE ABSENCE OF ADDED POLAR MATERIAL TO PRODUCE A MULTIFUNCTIONAL POLYMERIZATION INITIATOR.

United States Patent lice 3,640,899 Patented Feb. 8, 1972 REACTIONPRODUCT OF HYDROCARBYLMONO- LITHIUM AND 1,3-BUTADIENE AS POLYMERI-ZATION INITIATOR Floyd E. Naylor, Bartlesville, Okla., assiguor toPhillips Petroleum Company No Drawing. Filed Jan. 30, 1969, Ser. No.795,365 Int. Cl. C08d 3/06 US. Cl. 252-431 R 3 Claims ABSTRACT OF THEDISCLOSURE Secor tert-organomonolithium compounds are reacted with1,3-butadiene in the absence of added polar material to produce amultifunctional polymerization initiator.

This invention relates to a multifunctional polymerization initiatorwhich forms as a reaction product resulting from the reaction of1,3-butadiene and a secor tertorganomonolithium compound. In anotheraspect this invention relates to a polymerization process employingdilithium polymerization inititors. In another aspect this inventionrelates to a process for polymerizing isoprene to a highcis-polyisoprene. In still another aspect it relates to a process forpolymerizing conjugated dienes and mono vinyl substituted aromaticcompounds, and mixtures thereof.

Dilithium and monolithium polymerization initiators are well known tothe art. Many of these, however, require polar diluents for theirpreparation and they are often sufiiciently unstable that they cannot beprepared and subsequently stored for very long without a loss in theinitiator activity. Also insoluble initiators prepared in polarmaterials, even after repeated washings, may contain residual polarmaterial that can be undesirable in subsequent polymerization processes.Block copolymers of butadiene-styrene prepared by many of the well knownlithium initiators often exhibit low green tensile strengths.

It has now been discovered that a multifunctional polymerizationinitiator can be formed by reacting from 2 to 4 moles of a secortert-organomonolithium compound with one mole of 1,3-butadiene in theabsence of added polar material. The multifunctional polymerizationinitiators thus formed possess surprising versatile properties.

The multifunctional initiators produced according to this inventioncontain at least about two lithium atoms per molecule and areparticularly suited for the polymerization of isoprene to a highcis-polyisoprene. Block copolymers produced from styrene and butadieneexhibit high green tensile strengths when made according to thisinvention.

-It is an object of this invention to provide a new multilithium basedinitiator. It is another object of this invention to provide a processfor the polymerization of conjugated dienes and monovinyl-substitutedaromatic compounds and mixtures thereof. Other advantages and featuresof my invention will be apparent to those skilled in the art from thefollowing discussion and examples herein set forth.

According to my invention from 2 to 4 moles of a secortert-organomonolithium compound are reacted with one mole ofl,3-.butadiene in the absence of added polar material. The reaction canbe conducted in the presence or absence of an inert hydrocarbon diluent.The presence of an inert hydrocarbon diluent is preferred. Suitablediluents include aliphatic, cycloaliphatic and aromatic hydrocarbons.Aliphatic and cycloaliphatic hydrocarbons containing from 4 to 10 carbonatoms per molecule are preferred.

Exemplary of some suitable diluents, if employed, are butane, pentane,hexane, heptane, decane, cyclohexane, 1,2 dimethylcyclooctane, benzene,toluene, and the like and mixtures thereof. The amount of diluent thatcan be employed can vary over a wide range and can be convenientlydescribed in terms of molar concentration for the organomonolithiumcompound. This concentration can vary from 0.1 molar to that obtained inthe absence of diluent while the prefer-red range is from 1 molar to 4molar.

The organomonolithium, preferably hydrocarbyhnonolithium, compounds thatcan be employed in accordance with this invention can be represented bythe general formula RLi wherein R is a secor tert-alkyl, cycloalkyl, orarylalkyl hydrocarbon radical, or combinations thereof, containing from3 to 12 carbon atoms per molecule. Exemplary monolithium compounds thatcan be employed are isopropyllithium, sec-butyllithium,tert-butyllithium, cyclohexyllithium, cyclopentyllithium, 4phenylcyclohexyllithium, cyclopropyllithium, cyclooctyllithium, 1-methylcyclohexyllithium, 3,5 diethyl 3 octyllithium, 4 methyl 2pentyllithium, 3 phenyl-2hexyllithium, and the like. n-Butyllithium hasbeen found not acceptable in forming the multifunctional initiatorsaccording to this invention.

The temperatures employed for reacting the organomonolithium compoundwith 1,3-butadiene can vary from about 0 to 150 C. It is preferredhowever to react the compounds at a temperature from about 30 to C. Thepressure can also vary over a wide range. It is preferred, however, thatthe pressure be sufficient to maintain the reaction mixture in apredominantly liquid form. The time employed for the reaction can varyover a broad range and will generally depend upon the temperature andconcentration of the reactants employed. The range of time can be fromabout .10 seconds to 72 hours while the preferred range is from 0.25 to6 hours.

-.Multifunctiona1 initiators prepared according to this invention areessentially insoluble in the inert hydrocarbon reaction medium, if oneis employed. The insolubility of the initiator is a feature that can bean advantage inthat these initiators can be essentially freed of excessreactants by simple decantation. These insoluble components can thus bewashed with inert hydrocarbon and redispersed in an inert diluent foruse in polymerization runs.

Gas chromatography, mass spectrometer and mass digitizer analysis hasshown that the initiators produced according to this invention containat least about two lithium atoms per molecule of initiator. Theselithium substituents serve as reactive sites for polymerization atmultiple positions.

Various polymers can be prepared using initiators of this invention ashereinbefore stated. Homopolymers of conjugated dienes and copolymers oftwo 'or more conjugated dienes, homopolymers of monovinyl-substitutedaromatic compounds, copolymers of two or more monovinyl-substitutedaromatic compounds and copolymers of conjugated dienes withmonovinyl-substituted aromatic compounds can be prepared. Conjugateddienes having from 4 to 12 carbon atoms per molecule andmonovinylsubstituted aromatic compounds containing from 8 to 24 carbonatoms per molecule are preferred. Said mixtures of conjugated dieneswith monovinyl-substituted aromatic compounds can be employed at anyratio of the conjugated diene monomer to the monovinyl-substitutedaromatic monomer. Said mixtures of conjugated dienes with saidmonovinyl-substituted aromatic compounds can be polymerized bycontacting the entire mixture with the initiators of this invention oreach of the separate monomers can be added and polymerized essentiallyto completion prior to the addition of the subsequent monomer. Anydesired sequence of addition can be employed in the latter procedure.Examples of suitable monomers for use according to this inventioninclude 1,3 butadiene, isoprene, 1,3 pentadiene, 1,3- dodecadiene,styrene, 1 vinylnaphthalene, 4 methylstyrene, 4 vinylpyridine, and thelike. As hereinbefore stated, the multifunctional initiators of thisinvention are particularly suited for the polymerization of isoprene toa high cis-polyis'oprene. In the polymerization of isoprene, variousmodifiers known in the art can also be employed if desired when themultifunctional initiators of this invention are employed. U .8. Pat.3,278,508, Oct. 11, 1966, issued to Kahle et a1. and U.S. Pat.3,312,680, Apr. 4, 1967, issued to Kahle, disclose suitable modifiers.

Polymerization conditions generally known to the art can be suitablyemployed. The polymerization temperature can vary over a broad range andis generally from about -70 to 150 C.; it is preferred to operate at atemperature in the range of about 30 C. and above.

It is also preferred that the polymerization be conducted in thepresence of an inert diluent, such as those described for employment inthe initiator preparation process.

The polymerization process can also be conducted in the presence ofadded polar compounds such as amines, ethers, and the like, if desired.The amount of polar compound employed can vary over a wide range, butwill generally be in the range of about .01 to 100 parts of polarcompound per 100 parts of monomer employed.

The amount of multifunctional initiator to be employed in thepolymerization process ranges from about 0.25 to 200, preferably 1 to100 milliequivalents of lithium per 100 grams of monomers (meqhm.). Themilliequivalents of lithium can be conveniently determined by analkalinity titration of a known volume of reaction mixture containingthe multifunctional initiator. Said alkalinity titration employsstandardized acid, e.g., HCl, and an indicator such as phenolphthaleinto determine the end-point of the titration. The alkaline normality thusobtained provides a value for the milliequivalents of lithium permilliliter of reaction mixture containing the multifunctional initiator.

4 EXAMPLE I A multifunctional initiator was prepared employing thefollowing initiator preparation recipe:

Parts by weight Cyclohexane 175 Butadiene 100 sec-Butyllithium 237Temperature, C. 70 Time, hours 2 A solution of sec-butyllithium incyclohexane (about 1.5 M) was charged to the reactor first followed bythe addition of 1,3-butadiene. At the end of the reaction periodcyclohexane was removed from the insoluble initiator and was replaced byan equal volume of dry nhexane. This dispersion of initiator in n-hexanewas then employed for the polymerization of isoprene according to thefollowing polymerization recipe:

Parts by weight Isoprene 100 Cyclohexane 790 Initiator variable Modifier(n-butylbromide) variable Temperature, C 70 Time, hours 6 Cyclohexanewas charged to the reactor first followed by a nitrogen purge. Isoprenewas added next followed by the initiator dispersion. The temperature wasthen adjusted to 70 C. for the reaction period. In runs 1 and 2 themodifier was added after evidence of polymerization was noted by anincrease of the mixture viscosity, i.e., after 2-4 hours. At the end ofthe reaction period, each polymerization mixture was terminated by theaddition of a 10 weight percent solution of 2,2'-methylene-bis(4-methyl-6-tert-butylphenol) in a /50 by volume mixture by isopropylalcohol/toluene. The amount of this antioxidant solution added wassufficient to provide one part of the antioxidant per 100 parts ofpolymer. Each terminated mixture was stirred with isopropyl alcohol toprecipitate the polymer and the polymer from each run was separated anddried. The results of these polymerization runs are reported in Table I.These results demonstrate that the initiator of this invention can beemployed for the polymerization of isoprene to form a high cis-polymerand that modifiers can be employed to regulate the polymer molecularweight.

1 Milliequivalents of lithium expressed in terms of sec-butyllithium per100 grams monomer.

2 Gram millimoles per 100 grams of monomer.

3 Determined as described in U.S. Patent 3,215,679. Note (B), column 11.

4 Mierostructure determined as described in U.S. Patent 3,215,679. Note(A) ,eolumn ll. 6 Heterogeneity index.

The alkalinity concentration (normality) thus determined is thenemployed for charging a known quantity of milliequivalents of lithium inpolymerization recipes employing the multifunctional initiator of thisinvention.

The polymers prepared with the initiators of this invention can beemployed in the manufacture of automobile tires, tubing, belting,gaskets, shoe soles, containers and the like. They can also becompounded with known curing agents, fillers, plasticizers,antioxidants, stabilizers, and the like.

Illustrative of the foregoing discussion and not to be interpreted as alimitation on the materials herein employed, or on the scope of myinvention the following examples are herein provided.

EXAMPLE II Isoprene was polymerized with an initiator prepared accordingto initiator preparation recipe of Example I. The initiator was employedfor the polymerization of isoprene according to the followingpolymerization recipe:

Conversion, percent 1-.-..-

In this run cyclohexane was charged to the reactor first followed by anitrogen purge. Isoprene was added next followed by the tetraallyltinand then the initiator dispersion. Polymerization was terminated and thepolymer isolated as described in Example I. The raw polyisoprenecontained 85 percent unsaturation in the cis-1,4 configuration and 6.0percent in the 3,4-configuration. The polymer possessed an inherentviscosity of 5.14, and a Mooney viscosity, ML-4 at 212 F., of 76 and wasgel-free. The polyisoprene was then compounded employing the followingtire tread stock recipe:

Compounding recipe Parts, by weight Polyisoprene 100 IRB #2 a 50 Zincoxide 3 Stearic acid 3 Flexamine 1 Flexzone 3C 2 Philrich 5 d 5 Vu ltrole 1 Sulfur 2.25 NOBS Special 0.65

High abrasion furnace type carbon black.

Mixture containing 65 of a complex diarylamine-keton reaction productand 35 f N,N diphenyl-p-phenylenediam ne. A

c N-isopropyl-N-phenyl-p-pheny1enediamine.

Highly aromatic oil, Type 101 of ASTM D2226-63I.

N-nitrosodiphenylamine. N-oxydiethylene-2-benzothiazolesulfenamide.

TABLE II Processing data (BR--Banbury mixer) Mixing time, minutes 6.5Dump temperature, F. 300 Compounded Mooney (ML-4 212 F.) a 66 Extrusions250 F., Garvey Die inches/minute 70 grams/minute 118 Rating (3 to 12) 6Hand tack (0 to 10) 8 Dispersion, Cured (0 to 10) Physical properties(Cured 30 minutes at 293 F.)

300% Modulus, p.s.i. 1290 Tensile, p.s.i. 3580 Elongation, percent 630Max. Tensile 200 F., p.s.i 1880 AT, E 45 Resilience, percent 9 72 ShoreA Hardness 62 ASTM D1646-63.

h Ind. Eng. Chem.. 34, 1939 1942 ASTM D412-62T.

o ASTM 13945759.

The results in Table II of Example II demonstrate that a tread stockcompound with good properties was prepared from a polyisoprene initiatedwith a multifunctional initiator of this invention.

EXAMPLE III The initiator of Example I of this invention was employedfor the preparation of butadiene/styrene bl ock copolymers having highgreen tensile strength. The block copolymers were prepared according tothe following polymerization recipe:

6 Polymerization recipe 1,3-Butadiene, parts by weight 60 Styrene, partsby weight 40 Cyclohexane, parts by weight 790 Tetrahydrofuran (THF),parts by weight variable Initiator, meqhm. 5.0 Temperature, C. 70 Time,hours Butadiene polymerization variable Styrene polymerization 1 Inthese runs cyclohexane was charged to each reactor first followed by anitrogen purge. Butadiene was added next then THF and the initiator. Thetemperature was adjusted to 70 C. and the butadiene polymerized for thedesired time period. Styrene was then added and polymerized at 70 C. for1 hour. Each of the polymerizations were terminated and the polymersisolated as described in Example I. The polymerization results andpolymer properties are shown in Table III.

TABLE III Bd Pzn., Green Elonga- THF, time, Comm, tensile, tion, Run Nophm 2 hours percent LV. p.s.i. percent 4 1 1.0 2.0 2.10 3, l, 250 22.0 1. 5 100 2.17 2, 910 l, 350 3 3. 0 1. 0 100 2.01 2, 740 l, 000

1 1,3-bntadiene polymerization.

2 Parts by weight per 100 parts by weight of monomers. 3 Inherentviscosity. All polymers were gel-tree.

4 ASTM D 412-621.

A sample of the initiator prepared in Example I was placed in a tube andthe liquid phase removed under vacuum. The solid residue was hydrolyzedwith excess deuterium oxide (D O).The hydrocarbon products of thishydrolysis were analyzed by a gas chromatographmass spectrometermassspectrum digitizer combination. This analysis revealed that thehydrocarbon product of the above hydrolysis contained 70% by weight ofmonoolefins having eight carbon atoms and 30% by weight of saturatedhydrocarbons having 12 carbon atoms. Furthermore, the C monoolefinscontained on the average at least 1.7 deuterium atoms per molecule.Although the deuterium content of the C hydrocarbons could not bedetermined in this analysis, this product was obviously derived from theaddition of two moles of sec-butyllithium to one mole of 1,3-butadieneand thus would contain at least two lithiums per molecule of the Creaction product. Since the C monoolefins obtained on hydrolysis with D0 contained about two deuteriums per molecule, they were derived fromcompounds which also contained two lithiums per molecule. The C productin the reaction of sec-butyllithium with 1,3-butadiene was apparentlyderived from the addition of one mole of sec-butyllithium to one mole of1,3-butadiene followed by or subsequent to a metalation reaction inwhich a hydrogen of the 1,3- butadiene moiety was replaced by a lithiumatom.

The results of the above analysis demonstrate that the initiators ofthis invention contained at least about two lithiums per molecule ofinitiator.

As will be evident to those skilled in the art, various modifications ofthis invention can be made or followed,

in light of the discussion and disclosure herein set forth, withoutdeparting from the scope and spirit thereof.

I claim: 7

1. An essentially hydrocarbon insolublemultifunctional polymerizationinitiator which forms on admixing components consisting essentially of asecor tert-hydrocarbylmonolithium compound containing from 3 to 12carbon atoms per molecule and 1,3-butadiene wherein said admixing is inthe absence of added polar material and wherein 2 to 4 moles of saidhydrocarbylmonolithium compound are provided per mole of said1,3-butadiene, and wherein said admixing is conducted at a temperaturein the range of from about C. to 150" C. in the presence of an inerthydrocarbon diluent at a sufficient pressure to maintain the reactionmixture in a predominately liquid form and wherein said components areallowed to react in the range of from about seconds to 72 hours.

2. The multifunctional initiator of claim 1 wherein saidhydrocarbylmonolithium compound is represented by the formula RLiwherein R is a secor tert-alkyl, cycloalkyl, or arylalkyl radical, orcombinations thereof, and wherein about 2 moles of saidhydrocarbylmonolithium compound are provided per mole of 1,3-butadiene.

- 3. The multifunctional initiator of claim 2 wherein said admixing ofcomponents is conducted at a temperature in the range of to 0., saidcomponents are allowed to react in the range of. about 0.25 to 6 hours,and wherein said hydrocarbylmonolithium compound is sec-butyllithium andsaid inert hydrocarbon diluent is cyclohexane,

References Cited PATRICK P. GARVIN; Primary Examiner us. 01. X.R.260-94.2 M, 94.3

